I'm trying to fix a remote transmitter and think this may be the culprit; it rattles when shaken. The remote was dropped shortly before I noticed it stopped working, so that's my best guess. I fixed the remote one other time when the antenna broke off at the solder pad, and the solder joints for the crystal were broken. I've been soldering and tinkering for a long time but never worked with crystals. It looks like this one could be a 49U or UM-1 package. I searched DigiKey for a 27.147MHz crystal but couldn't find anything. How critical is it that the MHz match exactly? Do any of you have one of these you could sell? Any help is appreciated!

 

This is a plain crystal, not a complete oscillator, and the exact frequency is important. While lots of "standard" frequencies are available through distributors, non-standard parts like this one are very common in volume applications. ebay?

ak

 

That is a common xtal used in RC toys etc, you may be able to scrounge one off of a dud Txmtr.
Max.

 

or try International Crystal, in Oklahoma City. 27.145 is one of those rc chanels between the cb channels, so isnt as plentifull as the cb crystals.

 

Doubt its the Xtal,try resoldering it back on.

 

Hello,

When the crystal rattles when shaken, it could be broken.
The inside would look like in this add:
http://www.ecplaza.net/product/quartz-crystal-resonator-hc49u-49u--146610-1940597.html

As you can see there is a quartz plate with some small contacts mounted on it.

Bertus

 

I reinstalled the xtal and it still doesn't work. Here's the rest of the circuit in case you think it might be something else

 

"it rattles when shaken"
Replace it or make a little xtal checker. (Google)
In your second photo there is a solder blob you should remove.
It is where you soldered the xtal.



BTW, I have found that if you place a cap in series with the hot lead going to the xtal you can often test parallel coil/cap combinations for approximate frequency.
You do need a scope or freq. counter or radio.

 

Hi,

How critical is it that the MHz match exactly?

Any Citizens Band x-tal ch. 1..40 will be less than 1% off and as such, will have next to no impact on range in an IR remote control transmitter.

 

Since it rattles it is probably bad, so why not open it up? Do you have a Dremel tool and a cut off wheel? It may just be a broken connection that is fixable.

 

I contacted International Crystal MFG and they asked if I knew the load capacitance or had the schematic. Since I knew/had neither, they had an engineer look at the circuit pictures and their best guess would be 20pf. Then I would need to decide on whether it is fundamental or 3OT; any ideas?

I'll dremel mine open when I get some time

 

http://www.ecliptek.com/SpecSheetGenerator/specific.aspx?PartNumber=ECX-5605-27.147M

 

Yup, it's broken. I can't find any exact matches, the closest is 27.145. ICM could make one but it's pricy and may not be the correct load capacitance. Looks like I should just buy a new remote. Thanks for the help!

 

Doubt its the Xtal,try resoldering it back on.

Admittedly rare - but they do sometimes fail.

There's various crystal checker schematics floating about the web - usually one or 2 transistors and a small handful of resistors, capacitors etc.

 

Yup, it's broken. I can't find any exact matches, the closest is 27.145. ICM could make one but it's pricy and may not be the correct load capacitance. Looks like I should just buy a new remote. Thanks for the help!

View attachment 83242

Loading capacitors could be your salvation - if a standard crystal is cheap enough, try pulling its frequency by using 1 or 2 preferred values lower loading caps.

 

Try super glue.

 

Try super glue.

April 1st is over.

 

Hello,

The crystal is broken.
There is no way of mending it.
The superglue will not work, as the resonance is dependend on the size and thickness of the crystal.

Bertus

 

Try super glue.

There was a documentary about early home computers, there were several firms that offered their computers in kit form.

One recounted an occasion of a kit returned under warrantly to find out why it didn't work - it had been assembled perfectly, neatly and accurately - with polystyrene cement instead of solder!

 

There was a documentary about early home computers, there were several firms that offered their computers in kit form.

One recounted an occasion of a kit returned under warrantly to find out why it didn't work - it had been assembled perfectly, neatly and accurately - with polystyrene cement instead of solder!

That's a new one. Should go in the "Soldering for Dummies" instruction book.